|Publication number||US4736629 A|
|Application number||US 06/812,137|
|Publication date||Apr 12, 1988|
|Filing date||Dec 20, 1985|
|Priority date||Dec 20, 1985|
|Publication number||06812137, 812137, US 4736629 A, US 4736629A, US-A-4736629, US4736629 A, US4736629A|
|Inventors||John C. Cole|
|Original Assignee||Silicon Designs, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Non-Patent Citations (2), Referenced by (208), Classifications (10), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to accelerometers, and, in particular, to micro-miniature, solid state accelerometers that may be fabricated and mounted on a semiconductor substrate.
Micro-miniature, solid state accelerometers are used for a number of important applications, such as for acceleration sensors in missile safe and arm devices. One prior solid state accelerometer comprises a mass supported by a silicon beam upon which one or more piezoresistive sensing elements are formed. Under acceleration, the restoring force exerted by the beam on the mass induces stress in the sensing element. The resistance of the sensing element changes with the stress, and the change in resistance is converted to a differential voltage by using one or two sensing elements in a resistance bridge circuit.
The main problem with accelerometers using silicon piezoresistive sensing elements is temperature sensitivity. Doped silicon has a temperature coefficient of resistance of about several thousand parts per million per degree centigrade. The sensing elements therefore experience a change in resistance due to temperature changes as well as due to stress caused by acceleration. The temperature sensitivity of the output voltage can be reduced by completing the resistance bridge with resistors formed on the silicon beam adjacent to the sensing elements, but aligned such that they are insensitive to the stress. Although this arrangement works reasonably well, it nevertheless does not eliminate problems with temperature gradients across the silicon. In addition, the current through the bridge varies significantly over temperature, and trimming resistors located off the bridge must have temperature characteristics that track those of silicon.
Another prior solid state accelerometer design comprises a cantilevered beam of silicon dioxide fabricated on the surface of a silicon wafer and suspended over a well etched in the surface. A mass of metal is deposited on one side of the beam to provide sufficient sensitivity to acceleration. However, in this design the center of mass is offset from the centerline plane of the beam, thereby creating a sensitivity to accelerations in directions other than the intended sensitive direction.
Another prior solid state accelerometer design comprises a semiconductor flap member fixed to one side of a torsion bar. An electrode is located on a separate substrate that is attached to the flap member after fabrication. Acceleration is measured by comparing the variable capacitance between the electrode and the flap member with a fixed capacitance. This design has a number of drawbacks. Semiconductor materials such as silicon and silicon dioxide have relatively low densities. An inertial element made from silicon or silicon dioxide therefore has less mass and is less sensitive to acceleration than one of equal size made from heavier materials such as metals. Further drawbacks are that the voltage that must be applied to the variable capacitor to measure the capacitance creates an electrostatic force on the movable flap member that disturbs the value being measured. A further undesirable feature of this design is that the accelerometer requires the fabrication and assembly of two separate substrates. In addition, comparison of a variable with a fixed capacitance can introduce temperature sensitivities if the thermal coefficients of the two capacitors are not carefully matched. Finally, attachment of a torsion bar at two different locations onto a substrate of a material with a different thermal coefficient of expansion can introduce changes in longitudinal stress in the torsion bar due to changes in temperature, and such stress changes can result in a temperature sensitive scale factor for the accelerometer.
The present invention provides a micro-miniature, solid state accelerometer that overcomes the limitations of the prior solid state accelerometers described above.
In one aspect, the accelerometer of the present invention comprises a substrate, a sensing element comprising a metallic member, and mounting means for mounting the sensing element such that the sensing element is positioned above the substrate and can rotate about a flexure axis that is above and substantially parallel to the substrate. The flexure axis divides the sensing element into first and second sections. The total moment (mass times moment arm) of the first section about the flexure axis is different from the total moment of the second section about the flexure axis, such that acceleration normal to the substrate tends to rotate the sensing element about the flexure axis. A first electrode is mounted by the substrate adjacent the first section of the sensing element, the first electrode and first section together forming a first capacitor. Similarly, a second electrode is mounted by the substrate adjacent the second section of the sensing element, and the second electrode and the second section of the substrate together form a second capacitor. Detection means is provided coupled to the first and second capacitors for sensing rotation of the sensing element about the flexture axis.
The sensing element preferably comprises a metallic plate, and the substrate preferably comprises a semiconductor. The metal plate may include an internal opening, and the mounting means may comprise a pedestal mounted to the substrate and positioned within the opening, together with flexible support means connected between the metal plate and pedestal. In one embodiment, the support means comprises a pair of torsion members extending in opposite directions from the pedestal to the sensing element, the torsion members defining the flexure axis. In a second embodiment, the support means comprises a beam extending between the sensing element and pedestal in a direction parallel to the sensing element and substrate and perpendicular to the flexure axis. In a third embodiment, the support means comprises a box element surrounding the pedestal, a beam extending between the pedestal and box element, and a pair of torsion members extending in opposite directions from the box element to the sensing element.
In another aspect, the present invention provides a high g accelerometer that includes a plate member mounted above a substrate by a pedestal that divides the plate member into first and second cantilevered beams. The first and second fixed plates are positioned in the substrate adjacent the respective beams to form first and second capacitors. In response to acceleration normal to the substrate, the beams flex in the same direction, thereby varying the capacitance of the first and second capacitors. The fixed plates and beams are positioned and arranged such that the capacitances of the first and second capacitors are changed by different amounts in response to an acceleration. In a preferred embodiment, such differential change is accomplished by providing different total moments for the beams about the pedestal.
In another aspect, the present invention provides an accelerometer that includes an inertial mass, mounting means for mounting the inertial mass such that the inertial mass tends to move in response to acceleration along a sensitive axis, and first and second capacitors associated with the inertial mass, each capacitor comprising first and second plates. When the inertial mass moves, the capacitances of the first and second capacitors change by unequal amounts. The accelerometer further includes detection means for measuring the relative capacitances of the first and second capacitors, and for providing a corresponding output signal. The detection means includes an output terminal at which the output signal is produced, means for providing first and second reference voltages, an inverting amplifier having its input connected to the output terminal, an integrator having its output connected to the output terminal, and first, second and third switches. Each switch has a common terminal and A and B terminals. The common terminal of the first switch is connected to the first plates of the first and second capacitors. The A terminal of the first switch is connected to receive the first reference voltage, and the B terminal of the first switch is connected to the input of the integrator. The common terminal of the second switch is connected to the second plate of the first capacitor, the A terminal of the second switch is connected to the output of the inverting amplifier, and the B terminal of the second switch is connected to receive the second reference voltage. The common terminal of the third switch is connected to the second plate of the second capacitor, the A terminal of the third switch is connected to the second reference voltage, and the B terminal of the third switch is connected to the output terminal. Means are provided for causing the first, second and third switches to periodically change in concert between state A, wherein all switches have their common terminals connected to their A terminals, and state B wherein all switches have their common terminals connected to their B terminals.
FIG. 1 is a perspective view of a first preferred embodiment of the accelerometer of the present invention.
FIG. 2 is a perspective view of a second preferred embodiment of the accelerometer of the present invention.
FIG. 3 is a top plan view of a third embodiment of the accelerometer.
FIG. 4 is a top plan view of a fourth embodiment of the accelerometer.
FIG. 5 is a cross-sectional view of a fifth embodiment of the accelerometer.
FIG. 6 is a top plan view of the accelerometer of FIG. 5.
FIG. 7 is a circuit diagram of the detector.
One preferred embodiment of the accelerometer of the present invention is illustrated in FIG. 1. The accelerometer comprises movable plate 10 that is mounted above substrate 12 by mounting system 14. An internal area of movable plate 10 is removed to form opening 16. Mounting system 14 comprises pedestal 18 and torsion bars 20 and 22 positioned within opening 16, the torsion bars extending in opposite directions from the pedestal to the movable plate. Movable plate 10, pedestal 18 and torsion bars 20 and 22 are all fabricated from metal. The torsion bars define flexure axis 26 about which movable plate 10 can rotate with respect to pedestal 18 and substrate 12. Movable plate 10 and the upper surface 24 of substrate 14 are substantially planar, and mounting system 14 mounts movable plate 10 such that it is spaced above upper surface 24 and is parallel to the upper surface in the absence of acceleration normal to the upper surface.
Flexure axis 26 divides movable plate 10 into a first section 28 on one side of the flexure axis and a second section 30 on the opposite side of the flexure axis. The movable plate is constructed such that the total moment (i.e., mass times moment arm) of section 28 about flexure axis 26 is less than the total moment arm of section 30 about the flexure axis, i.e., the center of mass of the movable plate is offset (to the right in FIG. 1) from the flexure axis. Therefore in response to acceleration normal to upper surface 24, the movable plate tends to rotate about flexure axis 26, the degree of rotation being approximately proportional to the magnitude of the acceleration, and the direction of rotation corresponding to the direction of the acceleration, i.e., to whether the acceleration is directed into or out of the upper surface.
Substrate 12 comprises semiconductor layer 32 (only the upper portion of which is shown) covered by thin insulating layer 34. Semiconductor layer 32 normally comprises a silicon wafer upon which the electronics associated with the accelerometer are also fabricated, using conventional integrated circuit technology. Insulating layer 34 may comprise glass, silicon nitride, or any other suitable material compatible with integrated circuit technology. Conductive electrode or fixed plate 36 is formed in the upper surface of semiconductor layer 32 and is positioned underlying a portion of movable plate section 28. Conductive fixed plate 38 is also formed in the upper surface of semiconductor layer 32, and underlies a portion of movable plate section 30. Fixed plates 36 and 38 are preferably equal to one another in size and shape, and are preferably positioned symmetrically with respect to flexure axis 26.
Conductors 40, 42 and 44 are also formed in the upper surface of the semiconductor layer, and provide electrical connections to fixed plate 36, movable plate 10 and fixed plate 38, respectively. An opening is provided in insulating layer 34 underlying pedestal 18 to permit electrical contact between the pedestal and conductor 42. Fixed plates 36 and 38 and conductors 40, 42 and 44 are preferably fabricated at the same time as the associated electronic components using one or more conductive layers (e.g., polysilicon) of the integrated circuit process. As described below, fixed plate 36 and movable plate 10 form a first capacitor, and movable plate 10 and fixed plate 38 form a second capacitor. When movable plate 10 rotates about flexure axis 26 in response to acceleration, the capacitances of the first and second capacitors change in opposite directions, and such capacitance changes are detected and used to determine the direction and magnitude of the acceleration.
The sensitivity of the accelerometer illustrated in FIG. 1 is adjustable over a wide range by changing the geometry of movable plate 10 so as to vary its mass and the moment arms of sections 28 and 30 about flexure axis 26. The sensitivity may also be varied by varying the dimensions (and therefore the spring constants) of torsion bars 20 and 22. For a given movable plate and torsion bar geometry, the sensitivity of the accelerometer is increased by selecting a dense material with which to fabricate movable plate 10. Metals such as gold, iron and nickel are more dense than silicon and exert a larger force and torque for a given acceleration, thereby producing a larger deflection of movable plate 10 as compared with the deflection of a similar movable plate made of silicon. Furthermore, by achieving a center of inertial mass in the plan of the flexure axis, the accelerometer is virtually insensitive to accelerations parallel to upper surface 24.
In order to measure a cpacitance, it is necessary to apply a voltage difference between the capacitor plates. The applied voltage causes an electrostatic force of attraction between the plates. If this force causes a deflection that results in a change in capacitance, the process of measuring the capacitance disturbs the value of capacitance being measured. If the applied voltage is large enough and the capacitor spacing is sufficiently small, the resulting force will overcome the restoring force of the mounting system, causing the capacitor plates to pull together, rendering the device inoperative. This consideration sets the lower limit for sensitivity that can be achieved. An advantage of the accelerometer of the present invention is that fixed plates 36 and 38 are located such that the torque around flexure axis 26 caused by the voltage applied to fixed plate 36 tends to cancel the torque produced by the voltage on fixed plate 38. This canceling effect reduces or eliminates any perturbing deflections caused by the measuring voltages. A further advantage of using two variable capacitors located on opposite sides of a flexure axis is that the differential capacitance provides an output that is twice as sensitive as compared to a device using a single variable capacitor and a fixed capacitor. Furthermore, since each capacitor is composed of plates having identical composition, thermal coefficients of the capacitors will be essentially identical, a feature that eliminates a source of temperature sensitivity.
A further important advantage of the accelerometer of FIG. 1 is that it is relatively insensitive to differential thermal expansion or contraction. Movable plate 10 and mounting system 14 are composed of metal, whereas substrate 12 is principally composed of a semiconductor material such as silicon. The coefficient of thermal expansion of metal is significantly greater than that of silicon. Therefore as the temperature changes, the dimensions of movable plate 10 and mounting system 14 will change to a greater extent than the dimensions of substrate 12. By supporting the movable plate from a single, comparatively small pedestal 18, movable plate 10 and torsion bars 20 and 22 can expand and contract relative to substrate 12 without inducing stresses in the torsion bars that might affect the bias or sensitivity of the accelerometer.
A second preferred embodiment of the accelerometer of the present invention is shown in FIG. 2. This embodiment comprises movable plate 50 that is mounted above substrate 52 by mounting system 54. Movable plate 50 includes opening 56, and mounting system 54 comprises pedestal 58 and beam 60 formed within opening 56. Pedestal 58 is mounted to substantially planar upper surface 62 of substrate 52, and beam 60 extends parallel to the upper surface from pedestal 58 to movable plate 50. The pedestal and beam mount the movable plate such that it is spaced above upper surface 62 and parallel to the upper surface in the absence of acceleration normal to the upper surface. Movable plate 50 and mounting system 54 are composed of metal, and substrate 52 comprises semiconductor layer 70 and insulating layer 72.
In one embodiment, the center of mass of movable plate 50 is located at point 80 at the intersection of the movable plate and beam 60. It may be shown that in such an embodiment, movable plate 50 rotates about an apparent flexure axis 64 that is stationary in the plane of the plate and normal to the longitudinal axis of the beam 60, and that intersects the beam at a location spaced from pedestal 58 by a distance equal to one-third the length of the beam. Flexure axis 64 divides movable plate 50 into a first section 66 on one side of the flexure axis and a second section 68 on the opposite side of the flexure axis. Because the center of mass of the movable plate is positioned at point 80, the total moment of section 66 about flexure axis 64 is greater than the total moment of section 68 about flexure axis 64. The movable plate therefore rotates about the flexure axis in response to acceleration normal to upper surface 62. In the beam support embodiment of FIG. 2, other geometries for movable plate 50 may be used, so long as the center of mass of the movable plate remains offset to one side of the apparent flexure axis as the movable plate rotates in response to acceleration.
Fixed plate 74 is formed in the upper surface of semiconductor layer 70, and is positioned underlying a portion of movable plate section 66. Fixed plate 76 is also formed in the upper surface of semiconductor layer 70 and underlies a portion of movable plate section 68. The fixed plates are preferably equal to one another in size and shape, and symmetrically positioned with respect to flexure axis 64. However, plates that are of different sizes and/or asymmetrically positioned plates may also be used. Conductors 74, 76 and 78 are also formed in the upper surface of the semiconductor layer, and provide electrical connections to fixed plate 74, movable plate 50, and fixed plate 76, respectively. Fixed plate 74 and movable plate 50 form a first capacitor, and movable plate 50 and fixed plate 76 form a second capacitor. Changes in the values of these capacitors are sensed to measure acceleration as described below.
A third embodiment of the accelerometer of the present invention is illustrated in partial plan view in FIG. 3. This embodiment comprises movable plate 90 that is mounted above and parallel to the planar upper surface of a substrate by a mounting system that comprises pedestals 92 and 94 and torsion bars 96 and 98. Pedestals 92 and 94 are mounted to the upper surface of the substrate on opposite sides of movable plate 90. Torsion bar 96 extends from pedestal 92 to movable plate 90, and torsion bar 98 extends from pedestal 94 to movable plate 90. Torsion bars 96 and 98 are aligned with one another, such that they together mount the movable plate for rotation about flexure axis 100. The flexure axis divides movable plate 90 into section 102 on one side of the flexure axis and section 104 on the opposite side of the flexure axis. The total moment of section 102 about flexure axis 100 is greater than the total moment of section 104 about the flexure axis, such that the movable plate rotates in response to accelerations normal to the upper surface of the substrate. Fixed plates 106 and 108 underlie portions of sections 102 and 104 respectively, to form first and second capacitors. Electrical connections to fixed plate 106, movable plate 90 and fixed plate 108 are via conductors formed in the upper surface of the substrate.
In comparing the accelerometers shown in FIGS. 1-3, it will be noted that the accelerometer of FIG. 3 is mounted by two pedestals on opposite sides of the movable plate. As a result of this arrangement, temperature changes will cause the metal comprising the pedestals, torsion bar and movable plate to expand or contract to a greater extent than the substrate. As a result, temperature changes will introduce some stress changes in torsion bars 96 and 98. Thus, although the accelerometer shown in FIG. 3 possesses many of the advantages of the accelerometers shown in FIGS. 1 and 2, the accelerometer of FIG. 3 will be unsuitable for certain applications in which such stress results in unacceptable changes to the bias or sensitivity of the accelerometer.
A fourth embodiment of the accelerometer of the present invention is illustrated in partial plan view in FIG. 4. The embodiment of FIG. 4 includes movable plate 110 that is mounted above and parallel to the planar upper surface of a substrate by a mounting system that is in part a composite of the mounting systems shown in FIGS. 1 and 2. The mounting system in FIG. 4 is located within rectangular opening 126 of movable plate 110, and includes pedestal 112 mounted to the upper surface of the substrate, beam 114, box structure 116 and torsion bars 118 and 120. Beam 114 is connected between box structure 116 and overhanging lip 122 that extends from and is attached to pedestal 112. Torsion bars 118 and 120 connect opposite sides of box structure 116 to movable plate 110 to thereby define flexure axis 124 about which the movable plate may rotate. The movable plate is constructed such that flexure axis 124 divides the movable plate into a first section 128 on one side of the flexure axis and a section portion 130 on the opposite side of the flexure axis. The total moment of section 128 about the flexure axis is greater than the total moment of section 130 about the flexure axis, such that the movable plate rotates in response to acceleration normal to the upper surface of the substrate. The embodiment of FIG. 4 also includes fixed plates 132 and 134 that form first and second capacitors in a manner identical to the embodiments of FIGS. 1-3.
A fifth embodiment of the accelerometer of the present invention is illustrated in FIGS. 5 and 6. This embodiment is especially adapted for very large acceleration (e.g., 30,000 g) applications. For such accelerations, it is difficult to get any structure to deflect in a direction opposite to the acceleration, i.e., a movable plate would bend rather than rotate about a flexure axis. The embodiment of FIGS. 5 and 6 includes plate member 140 that is mounted above and parallel to the planar surface 142 of substrate 144 by a mounting system that comprises pedestal 146. The pedestal extends for essentially the full width of the plate member, and divides the plate member into a cantilevered beam 148 to one side of the pedestal and a second cantilevered beam 150 to the opposite side of the pedestal. Beams 148 and 150 flex towards and away from substrate 144 in response to acceleration normal to surface 142. Fixed plate 156 is formed in substrate 144 underlying beam 148, and fixed plate 158 is formed in substrate 144 underlying beam 150. Fixed plate 156 and beam 148 form a first capacitor, and fixed plate 158 and beam 154 form a second capacitor. The fixed plates and beams are formed and positioned such that in response to an acceleration normal to upper surface 142, the first and second capacitors change by different amounts. This feature is preferably implemented by making fixed plates 156 and 158 equal in size and shape and equally distant from pedestal 146, and by forming beams 148 and 150 such that the total moments of the beams about the pedestal are different from one another. FIGS. 5 and 6 illustrate this arrangement, wherein the total moment of beam 150 is greater than the total moment of beam 148.
FIG. 7 sets forth a circuit diagram for a preferred detector for converting the capacitance changes of the accelerometers of FIGS. 1-6 into an output voltage signal V representing acceleration. In FIG. 7, variable capacitor CA represents the capacitance between the movable plate (or one of the beams of the embodiment of FIGS. 5 and 6) and one of the plates fixed in the substrate, while variable capacitor CB represents the capacitance between the movable plate (or the other beam) and the other fixed plate. The detector of FIG. 7 comprises switches 160, 162 and 164, integrator 166 and unity gain inverting amplifier 168. All of the detector components may be fabricated directly on the corresponding substrate, such as substrate 12 of FIG. 1, using transistors, capacitors and resistive elements of a conventional MOS integrated circuit technology. The detector of FIG. 7 also comprises DC voltage source 170 (schematically illustrated as a battery), the DC voltage source providing reference voltages VR and ground.
Switch 160 comprises a common terminal 172 and terminals labeled A and B, the significance of the A and B terminals being described below. Terminal 172 corresponds, for example, to conductor 40 in FIG. 1. Switch 162 includes common terminal 174 and A and B terminals. Terminal 174 corresponds to conductor 44 in FIG. 1. Switch 164 includes common terminal 176 and A and B terminals. Terminal 176 corresponds to conductor 42 in FIG. 1. Switches 160, 162 and 164 are periodically switched in concert from their A positions (detector state A) to their B positions (detector state B) and then back to their A positions. The switching takes place in response to a CLOCK signal provided by a clock generator (not shown), and the switching frequency is such that the detector remains in each state for a time long enough to allow the voltages in the circuit to settle to within a small fraction of their final values in each state. With the switches in their A positions, terminal 176 is grounded, terminal 172 is connected to the output of inverting amplifier 168, and terminal 174 is connected to voltage VR. The output of inverting amplifier 168 is the negative of the output voltage V of the circuit. When the switches are in their B positions, terminal 176 is connected to the input of integrator 166, terminal 172 is connected to voltage VR, and terminal 174 is at voltage level V. thus in state A, capacitor CA charges to a voltage -V and capacitor CB charges to a voltage VR . In state B, capacitor CA charges to voltage VR, and capacitor CB charges to voltage V. Thus for capacitor CA, the charge difference between states A and B is CA ·(VR -(-V)). Similarly for capacitor CB, the charge difference between states A and B is CB ·(V-VR). At steady state (V essentially constant over a clock signal period), there must be no net charge transferred into integrator 166 during state B, and since the input to the integrator acts as a virtual ground, one may write:
CA ·(VR +V)+CB ·(V-VR)=0(1)
Equation (1) may be rearranged to produce: ##EQU1## The detector of FIG. 7 is stable so long as the integration capacitor or other charge storage means of integrator 166 is large in comparison to capacitors CA and CB. The detector provides a low-pass filter having a cutoff frequency that depends upon the integration capacitor, the frequency of the CLOCK signal, and the sum CA +CB. The detector may therefore be implemented so as to reduce the sensitivity of the accelerometer output to vibration above a selected cut-off frequency.
The mechanical and electrical elements of the accelerometer of the present invention may be fabricated in a signal process, thereby avoiding the problems inherent in the final assembly of separately fabricated substrates or subsystems. With particular reference to the accelerometer shown in FIG. 1 and the detector shown in FIG. 7, silicon wafers containing the integrated circuit electronics for the detector as well as fixed plates 36 and 38, and conductors 40, 42 and 44 may be manufactured using, for example, a standard MOS process. The wafers are then passivated by the depositing insulating layer 34 (e.g., glass) over the top of the silicon wafer. An opening in layer 34 is provided where contact between pedestal 18 and conductor 42 is required by selective etching using hydrofluoric acid. Thin layers of chromium and nickel are deposited over the insulating layer. A spacer comprising a suitable metal is then deposited on the substrate using either a subtractive or additive photoresist process similar to those used in integrated circuit manufacture. The spacer is formed with a central opening. Gold, iron, nickel or another suitable metal is then deposited over the spacer so as to form the movable plate or plate member and the mounting system, the pedestal portion of the mounting system corresponding to the central opening in the spacer. The spacer is then etched away using an etchant that attacks the spacer material without damaging other materials used, leaving movable plate 10 unsupported except where torsion bars 20 and 22 are attached to pedestal 18. Finally, the conductive metal deposited over the substrate is etched away, except where it is covered by the pedestal, using an appropriate etchant.
As may be appreciated, the accelerometer of the present invention provides a number of significant advantages with respect to prior accelerometers. The accelerometer of the present invention may be fabricated on a silicon substrate using conventional integrated circuit technology and without the need for a separate assembly step for combining the mechanical and electrical components of the accelerometer. The use of metal for the movable plate or plate member provides a comparatively dense material for the inertial mass of the sensing element. The use of two capacitors on opposite sides of a flexure axis substantially cancels the electrostatic forces caused by the measuring voltages, thereby reducing a significant source of error. The use of two capacitors also makes possible a differential output that has increased sensitivity and decrease susceptibility to errors due to thermal coefficients of the capacitors. Finally, for a number of the embodiments illustrated herein, the use of a single pedestal reduces the sensitivity of the accelerometer to errors caused by differential thermal expansion between the metal plate and the silicon substrate.
While the preferred embodiments of the invention have been illustrated and described, it should be understood that variations will be apparent to those skilled in the art. Accordingly, the invention is not be limited to the specific embodiments illustrated and described, and the true scope and spirit of the invention are to be determined by reference to the following claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3226981 *||Oct 29, 1962||Jan 4, 1966||North American Aviation Inc||Condition responsive signal generator for producing a variable frequency signal|
|US3355952 *||Mar 31, 1965||Dec 5, 1967||North American Aviation Inc||Accelerometer with digital readout|
|US3478604 *||May 17, 1968||Nov 18, 1969||Us Army||Electronic solid-state accelerometer|
|US3498138 *||Sep 9, 1966||Mar 3, 1970||Litton Systems Inc||Accelerometer|
|US3528297 *||Aug 16, 1968||Sep 15, 1970||Us Army||Double cantilever accelerometer|
|US4306456 *||Mar 25, 1980||Dec 22, 1981||Thomson-Csf||Elastic wave accelerometer|
|US4342227 *||Dec 24, 1980||Aug 3, 1982||International Business Machines Corporation||Planar semiconductor three direction acceleration detecting device and method of fabrication|
|US4345474 *||Apr 9, 1980||Aug 24, 1982||Societe D'applications Generales D'electricite Et De Mecanique Sagem||Electrostatic accelerometer|
|US4430895 *||Feb 2, 1982||Feb 14, 1984||Rockwell International Corporation||Piezoresistive accelerometer|
|US4459849 *||Jan 31, 1983||Jul 17, 1984||The Bendix Corporation||Compact force measuring system|
|US4483194 *||Jun 24, 1982||Nov 20, 1984||Centre Electronique Horloger S.A.||Accelerometer|
|US4598585 *||Mar 19, 1984||Jul 8, 1986||The Charles Stark Draper Laboratory, Inc.||Planar inertial sensor|
|SU498557A1 *||Title not available|
|1||Corey, "Multi-Axis Clusters of Single-Axis Accelerometers with Coincident Centers of Angular Motion Insensitivity", presented at the 6th International Aerospace Symposium, Bedford, England, Mar. 23-26, 1970.|
|2||*||Corey, Multi Axis Clusters of Single Axis Accelerometers with Coincident Centers of Angular Motion Insensitivity , presented at the 6th International Aerospace Symposium, Bedford, England, Mar. 23 26, 1970.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4851080 *||Dec 14, 1988||Jul 25, 1989||Massachusetts Institute Of Technology||Resonant accelerometer|
|US4920801 *||Jul 21, 1988||May 1, 1990||The Marconi Company Limited||Accelerometer|
|US4945765 *||Aug 31, 1988||Aug 7, 1990||Kearfott Guidance & Navigation Corp.||Silicon micromachined accelerometer|
|US4945773 *||Mar 6, 1989||Aug 7, 1990||Ford Motor Company||Force transducer etched from silicon|
|US4967598 *||Aug 18, 1988||Nov 6, 1990||Fujitsu Limited||Acceleration sensor|
|US5016072 *||Mar 14, 1990||May 14, 1991||The Charles Stark Draper Laboratory, Inc.||Semiconductor chip gyroscopic transducer|
|US5045152 *||Jun 29, 1990||Sep 3, 1991||Ford Motor Company||Force transducer etched from silicon|
|US5054320 *||Mar 28, 1990||Oct 8, 1991||Societe D'applications Generales D'electricite Et De Mecanique Sagem||Pendulous accelerometer with electrostatic rebalancing|
|US5115291 *||Jul 12, 1991||May 19, 1992||Honeywell Inc.||Electrostatic silicon accelerometer|
|US5126812 *||May 23, 1990||Jun 30, 1992||The Charles Stark Draper Laboratory, Inc.||Monolithic micromechanical accelerometer|
|US5129983 *||Feb 25, 1991||Jul 14, 1992||The Charles Stark Draper Laboratory, Inc.||Method of fabrication of large area micromechanical devices|
|US5130660 *||Apr 2, 1991||Jul 14, 1992||International Business Machines Corporation||Miniature electronic device aligner using capacitance techniques|
|US5146389 *||Jul 22, 1991||Sep 8, 1992||Motorola, Inc.||Differential capacitor structure and method|
|US5203208 *||Apr 29, 1991||Apr 20, 1993||The Charles Stark Draper Laboratory||Symmetrical micromechanical gyroscope|
|US5216490 *||Aug 3, 1990||Jun 1, 1993||Charles Stark Draper Laboratory, Inc.||Bridge electrodes for microelectromechanical devices|
|US5220835 *||Sep 12, 1991||Jun 22, 1993||Ford Motor Company||Torsion beam accelerometer|
|US5239871 *||Dec 17, 1990||Aug 31, 1993||Texas Instruments Incorporated||Capacitive accelerometer|
|US5249465 *||Dec 11, 1990||Oct 5, 1993||Motorola, Inc.||Accelerometer utilizing an annular mass|
|US5314572 *||Apr 22, 1992||May 24, 1994||Analog Devices, Inc.||Method for fabricating microstructures|
|US5326726 *||Jun 21, 1993||Jul 5, 1994||Analog Devices, Inc.||Method for fabricating monolithic chip containing integrated circuitry and suspended microstructure|
|US5329815 *||Dec 19, 1991||Jul 19, 1994||Motorola, Inc.||Vibration monolithic gyroscope|
|US5331852 *||Dec 16, 1991||Jul 26, 1994||The Charles Stark Draper Laboratory, Inc.||Electromagnetic rebalanced micromechanical transducer|
|US5345823 *||Nov 12, 1991||Sep 13, 1994||Texas Instruments Incorporated||Accelerometer|
|US5345824 *||Mar 4, 1993||Sep 13, 1994||Analog Devices, Inc.||Monolithic accelerometer|
|US5349855 *||Apr 7, 1992||Sep 27, 1994||The Charles Stark Draper Laboratory, Inc.||Comb drive micromechanical tuning fork gyro|
|US5349858 *||Jan 28, 1992||Sep 27, 1994||Canon Kabushiki Kaisha||Angular acceleration sensor|
|US5352635 *||Jan 28, 1993||Oct 4, 1994||Tu Xiang Zheng||Silicon accelerometer fabrication method|
|US5357803 *||Apr 8, 1992||Oct 25, 1994||Rochester Institute Of Technology||Micromachined microaccelerometer for measuring acceleration along three axes|
|US5383364 *||Nov 6, 1992||Jan 24, 1995||Nec Corporation||Three-axis acceleration sensor variable in capacitance under application of acceleration|
|US5404749 *||Apr 7, 1993||Apr 11, 1995||Ford Motor Company||Boron doped silicon accelerometer sense element|
|US5408119 *||Oct 17, 1990||Apr 18, 1995||The Charles Stark Draper Laboratory, Inc.||Monolithic micromechanical vibrating string accelerometer with trimmable resonant frequency|
|US5408877 *||Mar 16, 1992||Apr 25, 1995||The Charles Stark Draper Laboratory, Inc.||Micromechanical gyroscopic transducer with improved drive and sense capabilities|
|US5417111 *||Jun 10, 1993||May 23, 1995||Analog Devices, Inc.||Monolithic chip containing integrated circuitry and suspended microstructure|
|US5473946 *||Sep 9, 1994||Dec 12, 1995||Litton Systems, Inc.||Accelerometer using pulse-on-demand control|
|US5488864 *||Dec 19, 1994||Feb 6, 1996||Ford Motor Company||Torsion beam accelerometer with slotted tilt plate|
|US5496436 *||Jun 15, 1994||Mar 5, 1996||The Charles Stark Draper Laboratory, Inc.||Comb drive micromechanical tuning fork gyro fabrication method|
|US5505084 *||Mar 14, 1994||Apr 9, 1996||The Charles Stark Draper Laboratory, Inc.||Micromechanical tuning fork angular rate sensor|
|US5507911 *||Apr 14, 1995||Apr 16, 1996||The Charles Stark Draper Laboratory, Inc.||Monolithic micromechanical vibrating string accelerometer with trimmable resonant frequency|
|US5511421 *||Jul 8, 1993||Apr 30, 1996||Rohm Co., Ltd.||Acceleration sensor|
|US5515724 *||Apr 20, 1995||May 14, 1996||The Charles Stark Draper Laboratory, Inc.||Micromechanical gyroscopic transducer with improved drive and sense capabilities|
|US5528520 *||Dec 8, 1994||Jun 18, 1996||Ford Motor Company||Calibration circuit for capacitive sensors|
|US5581035 *||Aug 29, 1994||Dec 3, 1996||The Charles Stark Draper Laboratory, Inc.||Micromechanical sensor with a guard band electrode|
|US5587518 *||Dec 23, 1994||Dec 24, 1996||Ford Motor Company||Accelerometer with a combined self-test and ground electrode|
|US5591910 *||Jun 3, 1994||Jan 7, 1997||Texas Instruments Incorporated||Accelerometer|
|US5605598 *||May 13, 1994||Feb 25, 1997||The Charles Stark Draper Laboratory Inc.||Monolithic micromechanical vibrating beam accelerometer with trimmable resonant frequency|
|US5610335 *||May 19, 1994||Mar 11, 1997||Cornell Research Foundation||Microelectromechanical lateral accelerometer|
|US5610337 *||Mar 9, 1995||Mar 11, 1997||Texas Instruments Incorporated||Method of measuring the amplitude and frequency of an acceleration|
|US5620931 *||Jun 6, 1995||Apr 15, 1997||Analog Devices, Inc.||Methods for fabricating monolithic device containing circuitry and suspended microstructure|
|US5629243 *||Sep 14, 1995||May 13, 1997||Tokyo Gas Co., Ltd.||Preloaded linear beam vibration sensor and its manufacturing method|
|US5629629 *||Apr 4, 1996||May 13, 1997||Siemens Aktiengesellschaft||Circuit arrangement for determining differences in capacitance|
|US5635639 *||Jun 7, 1995||Jun 3, 1997||The Charles Stark Draper Laboratory, Inc.||Micromechanical tuning fork angular rate sensor|
|US5635739 *||Apr 25, 1995||Jun 3, 1997||The Charles Stark Draper Laboratory, Inc.||Micromechanical angular accelerometer with auxiliary linear accelerometer|
|US5640133 *||Jun 23, 1995||Jun 17, 1997||Cornell Research Foundation, Inc.||Capacitance based tunable micromechanical resonators|
|US5644086 *||Oct 8, 1996||Jul 1, 1997||Tokyo Gas Co., Ltd.||Preloaded linear beam vibration sensor|
|US5646348 *||Sep 5, 1995||Jul 8, 1997||The Charles Stark Draper Laboratory, Inc.||Micromechanical sensor with a guard band electrode and fabrication technique therefor|
|US5650568 *||May 12, 1995||Jul 22, 1997||The Charles Stark Draper Laboratory, Inc.||Gimballed vibrating wheel gyroscope having strain relief features|
|US5661240 *||Sep 25, 1995||Aug 26, 1997||Ford Motor Company||Sampled-data interface circuit for capacitive sensors|
|US5725729 *||Aug 15, 1996||Mar 10, 1998||The Charles Stark Draper Laboratory, Inc.||Process for micromechanical fabrication|
|US5731520 *||Aug 14, 1996||Mar 24, 1998||Ford Global Technologies, Inc.||Acceleration sensing module with a combined self-test and ground electrode|
|US5737961 *||Mar 26, 1996||Apr 14, 1998||Trw Inc.||Method and apparatus for detecting operational failure of a digital accelerometer|
|US5748004 *||Mar 15, 1996||May 5, 1998||Analog Devices, Inc.||Reset switch for a micromachined device|
|US5760305 *||Feb 20, 1996||Jun 2, 1998||The Charles Stark Draper Laboratory, Inc.||Monolithic micromechanical vibrating beam accelerometer with trimmable resonant frequency|
|US5767405 *||Jan 11, 1996||Jun 16, 1998||The Charles Stark Draper Laboratory, Inc.||Comb-drive micromechanical tuning fork gyroscope with piezoelectric readout|
|US5777482 *||Jul 3, 1996||Jul 7, 1998||Siemens Aktiengesellschaft||Circuit arrangement and method for measuring a difference in capacitance between a first capacitance C1 and a second capacitance C2|
|US5783973 *||Feb 24, 1997||Jul 21, 1998||The Charles Stark Draper Laboratory, Inc.||Temperature insensitive silicon oscillator and precision voltage reference formed therefrom|
|US5817942 *||Feb 28, 1996||Oct 6, 1998||The Charles Stark Draper Laboratory, Inc.||Capacitive in-plane accelerometer|
|US5847280 *||May 23, 1995||Dec 8, 1998||Analog Devices, Inc.||Monolithic micromechanical apparatus with suspended microstructure|
|US5856722 *||Dec 23, 1996||Jan 5, 1999||Cornell Research Foundation, Inc.||Microelectromechanics-based frequency signature sensor|
|US5892153 *||Nov 21, 1996||Apr 6, 1999||The Charles Stark Draper Laboratory, Inc.||Guard bands which control out-of-plane sensitivities in tuning fork gyroscopes and other sensors|
|US5900550 *||Jun 16, 1997||May 4, 1999||Ford Motor Company||Capacitive acceleration sensor|
|US5905203 *||Sep 30, 1996||May 18, 1999||Temic Telefunken Microelectronic Gmbh||Micromechanical acceleration sensor|
|US5911156 *||Feb 24, 1997||Jun 8, 1999||The Charles Stark Draper Laboratory, Inc.||Split electrode to minimize charge transients, motor amplitude mismatch errors, and sensitivity to vertical translation in tuning fork gyros and other devices|
|US5914553 *||Aug 21, 1997||Jun 22, 1999||Cornell Research Foundation, Inc.||Multistable tunable micromechanical resonators|
|US5920013 *||Feb 7, 1997||Jul 6, 1999||Ford Motor Company||Silicon micromachine with sacrificial pedestal|
|US5952574 *||Apr 29, 1997||Sep 14, 1999||The Charles Stark Draper Laboratory, Inc.||Trenches to reduce charging effects and to control out-of-plane sensitivities in tuning fork gyroscopes and other sensors|
|US5969250 *||Jan 21, 1998||Oct 19, 1999||The Charles Stark Draper Laboratory, Inc.||Micromechanical accelerometer having a peripherally suspended proof mass|
|US5978972 *||Jun 11, 1997||Nov 9, 1999||Johns Hopkins University||Helmet system including at least three accelerometers and mass memory and method for recording in real-time orthogonal acceleration data of a head|
|US6000280 *||Mar 23, 1998||Dec 14, 1999||Cornell Research Foundation, Inc.||Drive electrodes for microfabricated torsional cantilevers|
|US6000287 *||Aug 28, 1998||Dec 14, 1999||Ford Motor Company||Capacitor center of area sensitivity in angular motion micro-electromechanical systems|
|US6000939 *||Feb 8, 1999||Dec 14, 1999||Ray; Isaac||Universal alignment indicator|
|US6009753 *||Dec 2, 1998||Jan 4, 2000||Analog Devices, Inc.||Monolithic micromechanical apparatus with suspended microstructure|
|US6041655 *||Oct 3, 1997||Mar 28, 2000||Alliedsignal, Inc.||Active cover accelerometer|
|US6073484 *||Jul 19, 1996||Jun 13, 2000||Cornell Research Foundation, Inc.||Microfabricated torsional cantilevers for sensitive force detection|
|US6082197 *||Aug 12, 1997||Jul 4, 2000||Zexel Corporation||Acceleration sensor|
|US6087638 *||Jul 10, 1998||Jul 11, 2000||Silverbrook Research Pty Ltd||Corrugated MEMS heater structure|
|US6091050 *||Nov 17, 1997||Jul 18, 2000||Roxburgh Limited||Thermal microplatform|
|US6128957 *||Jan 27, 2000||Oct 10, 2000||Alliedsignal||Active cover accelerometer|
|US6149190 *||Apr 3, 1998||Nov 21, 2000||Kionix, Inc.||Micromechanical accelerometer for automotive applications|
|US6170332||Apr 19, 2000||Jan 9, 2001||Cornell Research Foundation, Inc.||Micromechanical accelerometer for automotive applications|
|US6192757||Dec 6, 1999||Feb 27, 2001||Analog Devices, Inc.||Monolithic micromechanical apparatus with suspended microstructure|
|US6199874||Dec 7, 1995||Mar 13, 2001||Cornell Research Foundation Inc.||Microelectromechanical accelerometer for automotive applications|
|US6257062||Oct 1, 1999||Jul 10, 2001||Delphi Technologies, Inc.||Angular Accelerometer|
|US6291908||Oct 6, 1999||Sep 18, 2001||Trw Inc.||Micro-miniature switch apparatus|
|US6316948 *||Jul 1, 1998||Nov 13, 2001||Setra Systems, Inc.||Charge balance network with floating ground capacitive sensing|
|US6365442||Oct 4, 2000||Apr 2, 2002||Trw Inc.||Efficient method of making micro-miniature switch device|
|US6386032||Aug 1, 2000||May 14, 2002||Analog Devices Imi, Inc.||Micro-machined accelerometer with improved transfer characteristics|
|US6393914||Feb 13, 2001||May 28, 2002||Delphi Technologies, Inc.||Angular accelerometer|
|US6401535 *||Jan 27, 2000||Jun 11, 2002||Honeywell International, Inc.||Active cover accelerometer|
|US6666092||Feb 28, 2002||Dec 23, 2003||Delphi Technologies, Inc.||Angular accelerometer having balanced inertia mass|
|US6718826||Feb 28, 2002||Apr 13, 2004||Delphi Technologies, Inc.||Balanced angular accelerometer|
|US6761070||Jan 31, 2002||Jul 13, 2004||Delphi Technologies, Inc.||Microfabricated linear accelerometer|
|US6791931 *||Mar 16, 2001||Sep 14, 2004||Hewlett-Packard Development Company, L.P.||Accelerometer using field emitter technology|
|US6845670 *||Jul 8, 2003||Jan 25, 2005||Freescale Semiconductor, Inc.||Single proof mass, 3 axis MEMS transducer|
|US6854330||Oct 24, 2002||Feb 15, 2005||Nth Tech Corporation||Accelerometer and methods thereof|
|US6868726||Jan 18, 2001||Mar 22, 2005||Analog Devices Imi, Inc.||Position sensing with improved linearity|
|US6879056 *||Dec 29, 2000||Apr 12, 2005||Intel Corporation||Converting sensed signals|
|US6912902 *||Mar 26, 2003||Jul 5, 2005||Honeywell International Inc.||Bending beam accelerometer with differential capacitive pickoff|
|US6936492||Dec 10, 2004||Aug 30, 2005||Freescale Semiconductor, Inc.||Single proof mass, 3 axis MEMS transducer|
|US6955086||Dec 19, 2003||Oct 18, 2005||Mitsubishi Denki Kabushiki Kaisha||Acceleration sensor|
|US7022543 *||Feb 23, 2005||Apr 4, 2006||Honeywell International, Inc.||Capacitive pick-off and electrostatic rebalance accelerometer having equalized gas damping|
|US7121141 *||Jan 28, 2005||Oct 17, 2006||Freescale Semiconductor, Inc.||Z-axis accelerometer with at least two gap sizes and travel stops disposed outside an active capacitor area|
|US7140250||Jun 6, 2005||Nov 28, 2006||Honeywell International Inc.||MEMS teeter-totter accelerometer having reduced non-linearty|
|US7146856 *||Jun 7, 2004||Dec 12, 2006||Honeywell International, Inc.||Dynamically balanced capacitive pick-off accelerometer|
|US7194376||Apr 27, 2004||Mar 20, 2007||Delphi Technologies, Inc.||Circuit and method of processing multiple-axis sensor output signals|
|US7195393||May 31, 2002||Mar 27, 2007||Rochester Institute Of Technology||Micro fluidic valves, agitators, and pumps and methods thereof|
|US7210356||Feb 18, 2005||May 1, 2007||Caterpillar Inc||Physical agents directive dosimeter system|
|US7211923||Nov 10, 2003||May 1, 2007||Nth Tech Corporation||Rotational motion based, electrostatic power source and methods thereof|
|US7217582||Aug 24, 2004||May 15, 2007||Rochester Institute Of Technology||Method for non-damaging charge injection and a system thereof|
|US7250322||Mar 16, 2005||Jul 31, 2007||Delphi Technologies, Inc.||Method of making microsensor|
|US7280014||Mar 12, 2002||Oct 9, 2007||Rochester Institute Of Technology||Micro-electro-mechanical switch and a method of using and making thereof|
|US7287328||Aug 24, 2004||Oct 30, 2007||Rochester Institute Of Technology||Methods for distributed electrode injection|
|US7293460||Apr 19, 2005||Nov 13, 2007||Delphi Technologies, Inc.||Multiple-axis linear accelerometer|
|US7378775||Nov 12, 2003||May 27, 2008||Nth Tech Corporation||Motion based, electrostatic power source and methods thereof|
|US7398683 *||Feb 10, 2004||Jul 15, 2008||Vti Technologies Oy||Capacitive acceleration sensor|
|US7408236||Mar 1, 2007||Aug 5, 2008||Nth Tech||Method for non-damaging charge injection and system thereof|
|US7426863 *||Jun 16, 2006||Sep 23, 2008||Vti Technologies Oy||Method of manufacturing a capacitive acceleration sensor, and a capacitive acceleration sensor|
|US7610809||Jan 18, 2007||Nov 3, 2009||Freescale Semiconductor, Inc.||Differential capacitive sensor and method of making same|
|US7624638||Nov 1, 2007||Dec 1, 2009||Mitsubishi Electric Corporation||Electrostatic capacitance type acceleration sensor|
|US7736931||Jul 20, 2009||Jun 15, 2010||Rosemount Aerospace Inc.||Wafer process flow for a high performance MEMS accelerometer|
|US7796872||Jan 5, 2007||Sep 14, 2010||Invensense, Inc.||Method and apparatus for producing a sharp image from a handheld device containing a gyroscope|
|US7907838||May 18, 2010||Mar 15, 2011||Invensense, Inc.||Motion sensing and processing on mobile devices|
|US7934423||Dec 10, 2007||May 3, 2011||Invensense, Inc.||Vertically integrated 3-axis MEMS angular accelerometer with integrated electronics|
|US8020441||Feb 5, 2008||Sep 20, 2011||Invensense, Inc.||Dual mode sensing for vibratory gyroscope|
|US8047075||Jun 21, 2007||Nov 1, 2011||Invensense, Inc.||Vertically integrated 3-axis MEMS accelerometer with electronics|
|US8079262||Oct 26, 2007||Dec 20, 2011||Rosemount Aerospace Inc.||Pendulous accelerometer with balanced gas damping|
|US8096182 *||May 29, 2008||Jan 17, 2012||Freescale Semiconductor, Inc.||Capacitive sensor with stress relief that compensates for package stress|
|US8141424||Sep 12, 2008||Mar 27, 2012||Invensense, Inc.||Low inertia frame for detecting coriolis acceleration|
|US8176782||Apr 25, 2007||May 15, 2012||Panasonic Electric Works Co., Ltd.||Capacitive sensor|
|US8187902||Jul 9, 2008||May 29, 2012||The Charles Stark Draper Laboratory, Inc.||High performance sensors and methods for forming the same|
|US8250921||Jul 6, 2007||Aug 28, 2012||Invensense, Inc.||Integrated motion processing unit (MPU) with MEMS inertial sensing and embedded digital electronics|
|US8347717||Jan 8, 2013||Invensense, Inc.||Extension-mode angular velocity sensor|
|US8351773||Mar 11, 2011||Jan 8, 2013||Invensense, Inc.||Motion sensing and processing on mobile devices|
|US8368387||Oct 28, 2008||Feb 5, 2013||Mitsubishi Electric Corporation||Acceleration sensor|
|US8462109||Jun 16, 2009||Jun 11, 2013||Invensense, Inc.||Controlling and accessing content using motion processing on mobile devices|
|US8508039||May 8, 2008||Aug 13, 2013||Invensense, Inc.||Wafer scale chip scale packaging of vertically integrated MEMS sensors with electronics|
|US8534127||Sep 11, 2009||Sep 17, 2013||Invensense, Inc.||Extension-mode angular velocity sensor|
|US8539835||Mar 22, 2012||Sep 24, 2013||Invensense, Inc.||Low inertia frame for detecting coriolis acceleration|
|US8581308||Feb 17, 2005||Nov 12, 2013||Rochester Institute Of Technology||High temperature embedded charge devices and methods thereof|
|US8656778||Dec 30, 2010||Feb 25, 2014||Rosemount Aerospace Inc.||In-plane capacitive mems accelerometer|
|US8850890 *||Aug 3, 2011||Oct 7, 2014||Robert Bosch Gmbh||Inertial sensor and method for manufacturing an inertial sensor|
|US8850891 *||Nov 3, 2011||Oct 7, 2014||Robert Bosch Gmbh||Micromechanical component and manufacturing method for a micromechanical component|
|US8952832||Apr 21, 2008||Feb 10, 2015||Invensense, Inc.||Interfacing application programs and motion sensors of a device|
|US8960002||Apr 28, 2011||Feb 24, 2015||Invensense, Inc.||Vertically integrated 3-axis MEMS angular accelerometer with integrated electronics|
|US8997564||Jun 8, 2012||Apr 7, 2015||Invensense, Inc.||Integrated motion processing unit (MPU) with MEMS inertial sensing and embedded digital electronics|
|US9052194||Aug 13, 2013||Jun 9, 2015||Invensense, Inc.||Extension-mode angular velocity sensor|
|US9097524||Jan 30, 2012||Aug 4, 2015||Invensense, Inc.||MEMS device with improved spring system|
|US20010032508 *||Jan 18, 2001||Oct 25, 2001||Lemkin Mark A.||Position sensing with improved linearity|
|US20020131228 *||Mar 12, 2002||Sep 19, 2002||Potter Michael D.||Micro-electro-mechanical switch and a method of using and making thereof|
|US20020131356 *||Mar 16, 2001||Sep 19, 2002||Eldredge Kenneth J.||Accelerometer using field emitter technology|
|US20020182091 *||May 31, 2002||Dec 5, 2002||Potter Michael D.||Micro fluidic valves, agitators, and pumps and methods thereof|
|US20040035206 *||Mar 26, 2003||Feb 26, 2004||Ward Paul A.||Microelectromechanical sensors having reduced signal bias errors and methods of manufacturing the same|
|US20040079154 *||Dec 19, 2003||Apr 29, 2004||Mitsubishi Denki Kabushiki Kaisha||Acceleration sensor|
|US20040145271 *||Nov 12, 2003||Jul 29, 2004||Potter Michael D||Electrostatic based power source and methods thereof|
|US20040187578 *||Mar 26, 2003||Sep 30, 2004||Malametz David L||Bending beam accelerometer with differential capacitive pickoff|
|US20040216523 *||Feb 10, 2004||Nov 4, 2004||Tuomo Lehtonen||Capacitive acceleration sensor|
|US20050005698 *||Jul 8, 2003||Jan 13, 2005||Motorola Inc.||Single proof mass, 3 axis mems transducer|
|US20050044955 *||Aug 24, 2004||Mar 3, 2005||Potter Michael D.||Methods for distributed electrode injection and systems thereof|
|US20050097957 *||Dec 10, 2004||May 12, 2005||Motorola Inc.||Single proof mass, 3 axis mems transducer|
|US20050132803 *||Mar 26, 2004||Jun 23, 2005||Baldwin David J.||Low cost integrated MEMS hybrid|
|US20050139942 *||Feb 23, 2005||Jun 30, 2005||Honeywell International, Inc.||Capacitive pick-off and electrostatic rebalance accelerometer having equalized gas damping|
|US20050205966 *||Feb 17, 2005||Sep 22, 2005||Potter Michael D||High Temperature embedded charge devices and methods thereof|
|US20050235751 *||Apr 27, 2004||Oct 27, 2005||Zarabadi Seyed R||Dual-axis accelerometer|
|US20050240374 *||Apr 27, 2004||Oct 27, 2005||Zarabadi Seyed R||Circuit and method of processing multiple-axis sensor output signals|
|US20050268719 *||Jun 7, 2004||Dec 8, 2005||Honeywell International, Inc.||Dynamically balanced capacitive pick-off accelerometer|
|US20060048575 *||Nov 7, 2005||Mar 9, 2006||Kazunari Nishihara||Drop shock measurement system and acceleration sensor element used in the same|
|US20060169043 *||Jan 28, 2005||Aug 3, 2006||Mcneil Andrew C||Z-axis accelerometer with at least two gap sizes and travel stops disposed outside an active capacitor area|
|US20060185433 *||Jun 6, 2005||Aug 24, 2006||Honeywell International, Inc.||MEMS teeter-totter accelerometer having reduced non-linearty|
|US20060185434 *||Feb 18, 2005||Aug 24, 2006||Caterpillar Inc.||Physical agents directive dosimeter system|
|US20060207327 *||Mar 16, 2005||Sep 21, 2006||Zarabadi Seyed R||Linear accelerometer|
|US20060207328 *||Apr 19, 2005||Sep 21, 2006||Zarabadi Seyed R||Multiple-axis linear accelerometer|
|US20060211161 *||Mar 16, 2005||Sep 21, 2006||Christenson John C||Method of making microsensor|
|US20070074731 *||Oct 5, 2005||Apr 5, 2007||Nth Tech Corporation||Bio-implantable energy harvester systems and methods thereof|
|US20070152776 *||Mar 1, 2007||Jul 5, 2007||Nth Tech Corporation||Method for non-damaging charge injection and system thereof|
|US20080110260 *||Nov 1, 2007||May 15, 2008||Mitsubishi Electric Corporation||Acceleration sensor|
|US20080166115 *||Jan 5, 2007||Jul 10, 2008||David Sachs||Method and apparatus for producing a sharp image from a handheld device containing a gyroscope|
|US20080173091 *||Jan 18, 2007||Jul 24, 2008||Freescale Semiconductor, Inc.||Differential capacitive sensor and method of making same|
|US20090007661 *||Jul 6, 2007||Jan 8, 2009||Invensense Inc.||Integrated Motion Processing Unit (MPU) With MEMS Inertial Sensing And Embedded Digital Electronics|
|US20090107238 *||Oct 26, 2007||Apr 30, 2009||Rosemount Aerospace Inc.||Pendulous accelerometer with balanced gas damping|
|US20090145225 *||Dec 10, 2007||Jun 11, 2009||Invensense Inc.||Vertically integrated 3-axis MEMS angular accelerometer with integrated electronics|
|US20090184849 *||Apr 21, 2008||Jul 23, 2009||Invensense, Inc.||Interfacing application programs and motion sensors of a device|
|US20090193892 *||Feb 5, 2008||Aug 6, 2009||Invensense Inc.||Dual mode sensing for vibratory gyroscope|
|US20120031186 *||Feb 9, 2012||Johannes Classen||Inertial sensor and method for manufacturing an inertial sensor|
|US20120167681 *||Nov 3, 2011||Jul 5, 2012||Jochen Reinmuth||Micromechanical component and manufacturing method for a micromechanical component|
|DE3824695A1 *||Jul 20, 1988||Feb 1, 1990||Fraunhofer Ges Forschung||Micromechanical acceleration sensor with capacitive signal transformation, and method for producing it|
|DE19547642A1 *||Dec 20, 1995||Jun 27, 1996||Zexel Corp||Multi-axis acceleration sensor for motor vehicle system|
|EP0507338A1 *||Apr 3, 1992||Oct 7, 1992||Japan Aviation Electronics Industry, Limited||Support structure for an accelerometer of the oscillating type|
|EP0623825A1 *||Mar 28, 1994||Nov 9, 1994||Ford Motor Company||Accelerometer sense element|
|EP0638783A1 *||Jul 20, 1994||Feb 15, 1995||New Sd, Inc.||Rotation rate sensor with center mounted tuning fork|
|EP0718632A2 *||Nov 27, 1995||Jun 26, 1996||Ford Motor Company Limited||Torsion beam accelerometer|
|EP0721108A2 *||Dec 12, 1995||Jul 10, 1996||Texas Instruments Incorporated||Acceleration condition sensor apparatus|
|EP2514713A1||Apr 20, 2011||Oct 24, 2012||Tronics Microsystems S.A.||A micro-electromechanical system (MEMS) device|
|WO1991014285A1 *||Mar 14, 1991||Sep 19, 1991||Draper Lab Charles S||Semiconductor chip gyroscopic transducer|
|WO1995013546A1 *||Nov 10, 1994||May 18, 1995||Allied Signal Inc||Improvement of charge balancing detection circuit|
|WO1997034155A1 *||Mar 14, 1997||Sep 18, 1997||Analog Devices Inc||Reset switch for a micromachined device|
|WO2005017536A1 *||Jul 6, 2004||Feb 24, 2005||Freescale Semiconductor Inc||Single proof mass, 3 axis mems transducer|
|WO2006083376A1 *||Nov 30, 2005||Aug 10, 2006||Freescale Semiconductor Inc||Z-axis accelerometer with at least two gap sizes and travel stops disposed outside an active capacitor area|
|WO2007125961A1||Apr 25, 2007||Nov 8, 2007||Ryo Aoki||Capacitive sensor|
|WO2014102507A1||Dec 24, 2013||Jul 3, 2014||Tronic's Microsystems||Micro-electromechanical device comprising a mobile mass that can move out-of-plane|
|U.S. Classification||73/514.32, 324/678, 73/514.36, 324/661|
|International Classification||G01P15/125, G01P15/08|
|Cooperative Classification||G01P15/0802, G01P15/125|
|European Classification||G01P15/125, G01P15/08A|
|Dec 20, 1985||AS||Assignment|
Owner name: SILICON DESIGNS, INC., 13547 S.E. 27TH PLACE, BELL
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:COLE, JOHN C.;REEL/FRAME:004502/0399
Effective date: 19851218
|Sep 13, 1991||FPAY||Fee payment|
Year of fee payment: 4
|May 11, 1995||FPAY||Fee payment|
Year of fee payment: 8
|Jun 21, 1999||FPAY||Fee payment|
Year of fee payment: 12